The subject of retrieving wires or cables which are lost in a well has been much developed because of the substantial economic consequences. A well from which a wire cannot be recovered can be totally incapacitated. To recover the wire takes time and skill, and involves lost production and costly labor and equipment rental. It is not surprising, therefore, that many "fishing" tools for this purpose have been developed. What is perhaps surprising is that after so many years, even the best of these tools has important shortcomings. It is an object of this invention to provide an improved tool that overcomes at least some of these shortcomings.
For example, when a wire (a cable is sometimes herein referred to as a wire) is lost downhole, it generally packs in as a tangled, snarled mess. To grab this cable, one must either work on its upper end and engage it with some device at the lower end of the tool, or penetrate the snarl, and engage it with some device on the wall of the tool. Because wires and cables are relatively thin, and in the snarl are convoluted, fishing at the upper end of the snarl involves a great deal of luck. Luck is not a valid criterion for equipment design.
Tools have been designed which penetrate the snarl. Two examples are Carver U.S. Pat. Nos. 4,353,585 and 4,397,494. These tools have a body with an outer wall, which body is caused to penetrate the snarl. Edges project beyond the outer wall, and they are tripped by contact with the wire so as to retract toward the body and to grab and hold the wire so that it can be pulled up with the body. These useful tools suffer from the disadvantages that the catches can impede the passage of the body into the snarl, and that the retentive forces holding the wire to the tool are limited by the strength of the catch. It is an object of this invention to provide a retrieval tool which does not suffer from these disadvantages.